A. Fouling

Most fouling is dependent on temperature, and for a given duty an extended-surface exchanger has a lower fin metal temperature than the equivalent bare-tube unit, thus reducing the fouling rate. Also, the longitudinal flow means no dead "areas" where fouling may build up. Finally, when fouling does occur, the heat transfer rate decreases, which increases the fin efficiency, thus partially compensating for the loss in heat transfer.

B. Flexibility

Double pipe exchangers are often supplied as multiple units connected in a series-parallel combination. Should the (low rate be changed, one can add or remove parallel streams without affecting the velocities or temperatures.

C. Low-cost standby